Melanotan II: Melanocortin Receptor Agonist
A cyclic heptapeptide analogue of alpha-MSH, studied for melanogenesis and melanocortin receptor activation.
Quick Reference
| Research Dosage | 100-500mcg per administration |
|---|---|
| Frequency | Variable (individual response varies) |
| Administration | Subcutaneous injection |
| Reconstitution | 1-2mL bacteriostatic water per 10mg vial |
| Storage | Light-sensitive – protect from light, refrigerate |
| Stability | 8-12 weeks refrigerated when protected from light |
Melanotan II was developed at the University of Arizona in the early 1990s as a synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH). It activates multiple melanocortin receptors (MC1R, MC3R, MC4R, MC5R), which explains its diverse effects extending far beyond pigmentation.
The non-selective receptor activation profile means MT2 affects multiple physiological pathways: MC1R controls melanogenesis (the pigmentation pathway), MC3R and MC4R regulate appetite and energy homeostasis, and MC4R also influences sexual function. This multi-receptor activity is both what makes MT2 biologically interesting and what creates its complex effect profile.
Research Applications
Melanotan II is studied across multiple research domains due to its activity at several melanocortin receptor subtypes:
Melanogenesis Research
The primary research application involves MC1R activation and pigmentation mechanisms:
- Stimulation of melanocytes to produce eumelanin (brown/black pigment)
- Research into pigmentation mechanisms and genetic variations
- Photoprotection studies examining melanin's role in UV protection
- Skin cancer risk research related to pigmentation
- Tyrosinase activation pathways
- cAMP signalling in melanocytes
UV Protection Research
Melanin provides natural protection against ultraviolet radiation:
- Studies examining whether increased melanin reduces UV-induced DNA damage
- Photoprotection mechanism research
- Relationship between pigmentation and skin cancer risk
- Comparative studies across different skin phototypes
MC4R and Energy Homeostasis
MC4R is central to appetite and weight regulation pathways:
- Feeding behaviour research through central MC4R activation
- Energy expenditure studies
- Body composition research
- Appetite regulation mechanisms
- Metabolic pathway investigations
Sexual Function Research
MC4R activation affects sexual function through central nervous system pathways:
- CNS-mediated arousal mechanisms
- Separate research domain from pigmentation effects
- Led to development of PT-141 (Bremelanotide) as a more targeted analogue
MT2's broad receptor activity has made it valuable for understanding the melanocortin system's role across multiple physiological functions. The non-selective nature provides insights into receptor cross-talk and system-wide effects.
Dosage Information
Research Dosages
Dosages commonly referenced in research literature range from 100-500mcg per administration. Response varies significantly between individuals due to genetic factors.
Individual Variation Factors
Several factors contribute to highly variable responses:
- MC1R polymorphisms: Genetic variations in the MC1R gene significantly affect receptor function and response
- Skin type differences: Fitzpatrick skin types I-VI have different baseline melanocyte activity
- Receptor sensitivity: Individual variation in receptor density and downstream signalling
- Baseline pigmentation: Starting melanin levels influence observable changes
Administration
Research protocols typically utilise subcutaneous injection. The cyclic structure and protease resistance allow for effective absorption via this route. Gradual dosing approaches are common in research protocols to assess individual response patterns.
Reconstitution Guide
Required Materials
- Melanotan II lyophilised powder (10mg vial)
- Bacteriostatic water (water containing 0.9% benzyl alcohol)
- Sterile insulin syringe for reconstitution
- Alcohol swabs for sterile technique
Reconstitution Steps
- Allow the Melanotan II vial to reach room temperature before reconstitution
- Draw 1-2mL of bacteriostatic water into the syringe (1mL provides easier dose calculation)
- Insert the needle into the vial and direct the stream of water down the inside wall – do not spray directly onto the powder
- Allow the powder to dissolve naturally without shaking. Gentle swirling is acceptable if needed. The solution should be clear.
- Immediately store in a dark location – light exposure degrades MT2
- Refrigerate at 2-8°C immediately after reconstitution
Concentration Reference Table
| Vial Size | Water Added | Concentration | 100mcg Dose | 250mcg Dose | 500mcg Dose |
|---|---|---|---|---|---|
| 10mg | 1mL | 10mg/mL | 1 unit (0.01mL) | 2.5 units (0.025mL) | 5 units (0.05mL) |
| 10mg | 2mL | 5mg/mL | 2 units (0.02mL) | 5 units (0.05mL) | 10 units (0.1mL) |
Storage Guidelines – Critical
Light Sensitivity Warning: Melanotan II is highly sensitive to light degradation. Proper light protection is essential for maintaining peptide integrity and potency.
Lyophilised (Powder) Form
- Store in dark location – protect from all light exposure
- Refrigeration (2-8°C) recommended for optimal stability
- Freezing (-20°C) extends stability for long-term storage
- Keep vial sealed until ready for reconstitution
- Use original packaging or wrap in foil for additional light protection
Reconstituted Solution
- Must be stored in complete darkness – wrap vial in foil or store in opaque container
- Refrigerate at 2-8°C immediately after reconstitution
- Stable for 8-12 weeks when stored correctly away from light
- Do not freeze after reconstitution
- Minimise light exposure when drawing doses – work quickly
- Use amber vials if available for additional protection
- If solution becomes discoloured or contains particles, discard
Frequently Asked Questions
Common questions about Melanotan II research
Why does Melanotan II affect more than pigmentation?
Melanotan II activates multiple melanocortin receptors, not just MC1R which controls pigmentation. MC3R and MC4R activation affects appetite, energy homeostasis, and other physiological processes. This non-selective receptor profile is what gives MT2 its diverse range of biological effects beyond melanogenesis.
Why is light protection important for Melanotan II?
Melanotan II contains tryptophan and other amino acid residues that are photosensitive. Light exposure causes degradation of the peptide structure and reduced potency. Always store in a dark location, use amber vials if available, and minimise light exposure when drawing doses.
Why does response vary so much between individuals?
MC1R polymorphisms (genetic variations) significantly affect receptor function and response to melanocortin peptides. Different skin types have different baseline melanocyte activity and receptor density. This genetic variation means dosing must be individualised based on response.
What is the difference between Melanotan I and Melanotan II?
Melanotan I (afamelanotide) is a linear peptide that selectively targets MC1R for pigmentation research. Melanotan II is a cyclic peptide with broader receptor activity across MC1R, MC3R, MC4R, and MC5R. MT2's non-selective profile produces more diverse effects beyond pigmentation.
How does the cyclic structure benefit Melanotan II?
The cyclic structure created by the lactam bridge between Asp and Lys residues confers several advantages: increased resistance to enzymatic degradation (protease resistance), enhanced receptor binding affinity, and extended half-life compared to linear peptide analogues.
What is the molecular weight of Melanotan II?
Melanotan II has a molecular weight of 1024.18 g/mol (Daltons). It is a cyclic heptapeptide containing 7 amino acids with a lactam bridge.
How long does reconstituted Melanotan II remain stable?
When stored properly at 2-8°C and protected from light, reconstituted Melanotan II remains stable for 8-12 weeks. Light exposure significantly accelerates degradation, so dark storage is essential for maintaining potency.
What is MC1R and why is it important?
MC1R (Melanocortin 1 Receptor) is the primary receptor controlling melanogenesis – the production of melanin pigment in melanocytes. When activated by Melanotan II or natural alpha-MSH, MC1R triggers a signalling cascade that increases tyrosinase activity and melanin synthesis.
The Science: How Melanotan II Works
The Melanocortin System
The melanocortin system is a complex signalling network comprising five receptor subtypes (MC1R through MC5R), endogenous ligands (α-MSH, ACTH, and others), and regulatory proteins. This system controls diverse physiological functions from pigmentation to appetite to stress responses.
MT2's Receptor Profile
Unlike the natural hormone α-MSH, Melanotan II has been structurally modified to be:
- More potent: Structural modifications increase receptor binding affinity
- Longer-lasting: Cyclic structure resists enzymatic degradation
- Non-selective: Activates multiple melanocortin receptor subtypes (MC1R, MC3R, MC4R, MC5R)
Cyclic Peptide Structure
Melanotan II is a cyclic heptapeptide with unique structural features:
- Contains a lactam bridge between Asp and Lys residues
- This cyclisation confers protease resistance (enzymatic stability)
- Increases receptor binding affinity compared to linear analogues
- Extends biological half-life significantly
- The D-Phe substitution further enhances stability and potency
MC1R Activation and Melanogenesis
The pigmentation pathway through MC1R follows a defined signalling cascade:
- Receptor binding: MT2 binds to MC1R on melanocyte cell surface
- cAMP increase: Receptor activation stimulates adenylyl cyclase, increasing intracellular cAMP
- Tyrosinase activation: cAMP activates tyrosinase, the rate-limiting enzyme in melanin synthesis
- Melanin precursor conversion: Tyrosinase converts tyrosine to DOPA and subsequently to melanin precursors
- Eumelanin production: Increased synthesis of eumelanin (brown/black pigment) in melanosomes
Amino Acid Sequence and Structure
Full Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂
Structural Components
- Ac- (N-terminal): Acetyl group protecting the N-terminus
- Nle: Norleucine – non-natural amino acid replacing Met for stability
- cyclo[...]: Indicates the cyclic portion of the peptide
- D-Phe: D-isomer of phenylalanine – enhances receptor selectivity and stability
- Lactam bridge: Formed between Asp and Lys side chains
- -NH₂ (C-terminal): Amide group protecting the C-terminus
Technical Specifications
| Systematic Name | Melanotan II |
|---|---|
| Other Names | Melanotan 2, MT2, MT-2, MT-II, MTII, Melanotan-II |
| Amino Acid Count | 7 |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 |
| Molecular Formula | C50H69N15O9 |
| Molecular Weight | 1024.18 g/mol |
| CAS Number | 121062-08-6 |
| Appearance | White to off-white lyophilised powder |
| Solubility | Freely soluble in water and aqueous buffers |
| Purity (PurposeLabs) | ≥99% (HPLC verified) |
| Storage (Lyophilised) | -20°C long-term, 2-8°C short-term |
| Storage (Reconstituted) | 2-8°C, use within 4-6 weeks |
Quality: Australian University Testing
Why Peptide Quality Matters
The research peptide market contains products of highly variable quality. Independent testing of products from various suppliers has revealed significant issues:
- Purity levels as low as 50% in products claiming "99% purity"
- Incorrect amino acid sequences (entirely wrong peptides)
- Truncated sequences (missing amino acids)
- Bacterial endotoxin contamination
- Oxidised or degraded peptides with reduced activity
Our Testing Protocol
Every batch of Melanotan II from PurposeLabs undergoes comprehensive testing at a leading proteomics laboratory based at an Australian university in Sydney – one of Australia's premier analytical facilities.
Confirms purity levels of ≥99%, identifies any impurities or degradation products.
Verifies exact molecular weight, confirms correct amino acid sequence.
Determines actual peptide content versus salt, moisture, and counter-ions.
Why Australian University Testing?
Our testing partner is an established, verifiable proteomics facility at a major Australian university, with published research credentials, transparent methodology, and no commercial conflict of interest. This contrasts with overseas "certificates of analysis" from unknown or unverifiable laboratories.
Shop Melanotan II
Australian university tested. 99%+ purity verified by HPLC and mass spectrometry. Fast shipping from Sydney.
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References
Key studies for researchers seeking primary literature:
- Hadley ME, et al. "Discovery and development of novel melanogenic drugs. Melanotan I and II." Pharmaceutical Biotechnology, 1998.
- Dorr RT, et al. "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study." Life Sciences, 1996.
- Wessells H, et al. "Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study." Journal of Urology, 1998.
- Hruby VJ, et al. "Cyclic lactam alpha-melanotropin analogues of Ac-Nle4-cyclo[Asp5, D-Phe7, Lys10] alpha-melanocyte-stimulating hormone-(4-10)-NH2 with bulky aromatic amino acids at position 7 show high antagonist potency and selectivity at specific melanocortin receptors." Journal of Medicinal Chemistry, 1995.
- Cai M, et al. "The melanocortin receptor system: a target for multiple degenerative diseases." Current Protein and Peptide Science, 2016.
- Garcia-Borron JC, et al. "Melanocortin-1 receptor structure and functional regulation." Pigment Cell Research, 2005.
- Wikberg JE, et al. "New aspects on the melanocortins and their receptors." Pharmacological Research, 2000.
- Abdel-Malek ZA, et al. "The melanocortin 1 receptor and the UV response of human melanocytes – a shift in paradigm." Photochemistry and Photobiology, 2014.
Disclaimer
All products sold by PurposeLabs are intended for laboratory and research use only. They are not intended for human or animal consumption. The information provided is for educational purposes only and should not be construed as medical advice. Consult with qualified healthcare professionals for any health-related decisions.
Melanotan II is not approved by the TGA for therapeutic use in Australia. Products are sold strictly for research purposes in accordance with Australian regulations.